GG18 Threshold ECDSA

Status

Draft. Reference implementation: crates/confium-tc-gg18.

Motivation

GG18 (Gennaro & Goldfeder 2018) is a 4-round threshold ECDSA protocol. CMP20 supersedes GG18; use CMP20 for new deployments. GG18 is retained for interoperability with existing threshold systems.

Scope

• T-of-N threshold ECDSA over P-256
• Four rounds: key generation, pre-signing (two rounds), signing
• Paillier homomorphic encryption with MtA
• Identifiable abort via accusations

Out of scope

• New deployments — use CMP20 instead.

Specification

See CMP20 spec (70-cmp20) for the foundational MtA primitives. GG18 adds an extra pre-signing round to support identifiable abort.

References

• Gennaro, R., & Goldfeder, S. (2018). Fast Multiparty Threshold ECDSA with Fast Trustless Setup. ACM CCS 2018.
• Confium source: crates/confium-tc-gg18